1. Field of the Invention
This invention relates to a supporting mechanism or system for supporting an optical pickup device for writing and/or reading information signals on or from an optical recording medium, such as an optical disc, in a recording and/or reproducing apparatus, so that the optical pickup device may be supported for movement radially of the optical recording medium.
2. Description of Related Art
An optical recording medium, such as an optical disc, has been proposed as a recording medium for information signals. The information signals are written on and/or reproduced from the optical recording medium by the recording and/or reproducing apparatus.
The recording and/or reproducing apparatus for recording and/or reproducing information signals using the optical disc is made up of a rotating and driving device for rotationally driving the optical disc and an optical pickup device for radiating the light beam to the optical disc for writing and/or reading information signals on or from the disc. That is, in the recording and/or reproducing apparatus, the optical disc is rotationally driven by the rotating and driving device, while being irradiated with the light beam for writing and/or recording the information signals.
The optical pickup device is made up of a light source, such as a laser diode, an optical device for conducting the light beam from the light source to a predetermined light path, and an object lens for converging and radiating the light beam on the major surface of the disc which is its signal recording surface.
The optical pickup device of the recording and/or reproducing apparatus is supported by a supporting mechanism of the optical pickup device, in such a manner that, as shown in FIG. 1, the major surface of the optical disc 33 carrying the signal recording layer thereon is faced by its object lens 105a.
The light source and the optical device are housed within an optical block 104. The object lens 105a is supported with respect to the upper surface of the optical block 104 by means of an object lens driving unit 105 so that a converging point of the light beam is located at all times on the optical disc 33 which is rotationally driven by the rotating and driving unit while being subject to offsetting and deviation from the horizontal. The object lens driving unit 105 supports the object lens 105a for movement in a direction perpendicular to the major surface of the optical disc 33, that is in a direction along the optical axis of the object lens 105a, and in a direction normal to the optical axis of the object lens 105a, that is in a direction along the radius of the optical disc 33.
The supporting mechanism for the optical pickup device is comprised of first and second guide shafts 101, 102, mounted parallel to each other, and a plurality of supporting members mounted on the optical block 104 and abutted on the first and second guide shafts 101, 102 for supporting the optical block 104 with respect to the guide shafts 101, 102.
The supporting members mounted on the optical block 104 are comprised of first and second guide rollers 108, 109 mounted at a front side on a lateral surface of the optical block 104, third and fourth guide rollers, not shown, mounted at a rear side on the same lateral surface of the optical block 104, and fifth and sixth guide rolls 112, 115 mounted on the opposite lateral surface trace of the optical block 104.
The first and second guide rolls 108, 109 are rotatably supported by supporting shafts 108a, 109a, set on the optical block 104 at an angle of 90.degree. relative to each other. The third and fourth guide rollers (not shown) are rotatably supported by supporting shafts, not shown, set on the optical block 104 at an angle of 90.degree. relative to each other. The first guide roller 108 and the third guide roller are mounted with their axes parallel to each other. The second guide roller 109 and the fourth guide roller are also mounted with their axes parallel to each other. The first and second guide rollers 108, 109 are caused to bear against the first guide shaft 101 for engaging with the first guide shaft 101 in-between. The third and fourth guide rollers are also caused to bear against the first guide shaft 101 for engaging with the first guide shaft 101 in-between. That is, the optical block 104 is position-controlled by the first to fourth guide rollers so that only rotation of the optical block 104 about the first guide shaft 101 as a center of rotation and a movement along the axis of the first guide shaft 101 are allowed.
The fifth guide roller 112 is rotatably mounted on a supporting shaft 112a set on the opposite lateral surface of the optical block 104 obliquely upwardly at an angle of 45.degree.. The fifth guide roller 112 is caused to bear against the second guide shaft 102.
The sixth guide roller 115 is rotatably supported on a supporting shaft 115a set on a spring plate 113 mounted by a set screw 114 on the same opposite lateral surface of the optical block 104. The sixth guide roller 115 is supported by a supporting shaft 115a which is mounted obliquely downwardly at an angle of 90.degree. with respect to the supporting shaft 112a supporting the fifth guide roller 112.
The fifth and sixth guide rollers 112, 115 are caused to bear on the second guide shaft 102 for engaging with the second guide shaft 102. The sixth guide roller 115 is biased by spring plate 113 towards the second guide shaft 102 as shown by arrow a in FIG. 1. Under the force of reaction to the thrusting force of the sixth guide roller 115 against the second guide shaft 102, the optical block 104 is resiliently biased towards the first guide shaft 101, as shown by arrow b in FIG. 1.
The optical block 104 may be moved along the first and second guide shafts 101, 102, with the guide rollers in rolling contact with respect to these guide shafts. The direction of possible movement of the optical block 104 along the guide shafts 101, 102 is coincident with the radial direction of the optical disc rotationally driven by the rotating and driving unit.
The recording and/or reproducing apparatus, comprising the optical pickup device supported by the supporting system for the optical pickup device as described above, modulates the information signals supplied from outside the apparatus for recording the information signals on the optical disc by means of the optical pickup device. The recording and/or reproducing apparatus also demodulates the signals read out by the recording and/or reproducing apparatus for reproducing the information signals recorded on the optical disc 33.
In the above-described supporting system for the optical pickup device, the optical pickup device 104 tends to be rotated upwardly around the first guide shaft 101 as a center of rotation, as indicated by an arrow c in FIG. 2, under vibrations or impacts propagated from outside the recording and/or reproducing apparatus. At this time, the fifth guide roller 112 is separated from the second guide shaft 102. This is because the force of inertia produced in the optical block 104 under the above-mentioned impacts etc. becomes larger than the force of bias exerted by the spring plate 113.
If the optical block 104 is rotated in this manner upwardly around the first guide shaft 101, there is a risk that the object lens driving device 105 of the object lens 105a may contact with the optical disc 33. If the object lens 105 etc. contacts the optical disc 105 while the disc 33 is kept in rotation, not only is the smooth recording and/of reproduction of the information signals on or from the disc 33 impeded, but also the disc 33 or the object lens 105a etc. may be contaminated of damaged.
On the other hand, there are occasions wherein an adjustment opening etc. is provided in the lower surface of the optical block 104 in order to permit position adjustment within the optical block 104 of optical devices, not shown, provided within the optical block. Such position adjustment of the optical devices etc. via the adjustment opening is effected, using an adjustment jig, such as a screwdriver, from the underside of the optical block 104, while the optical disc 33 is kept in rotation. If, during such position adjustment, the optical block 104 is biased upwardly by the adjustment jig, there is a risk that the optical block 104 will be rotated around the first guide shaft 101, so as to be moved towards the optical disc 33, as shown in FIG. 2. In such case, the object lens driving device 105 of the object lens 105 may contact with the optical disc 33.